After looking through the comments here, I'll give you the benefit of the doubt and assume that you just don't understand what you're saying, because you seem to be under the impression that "defederating" means that noone that isn't subscribed to the defederating instance will have access to the content anymore. (e.g. Instance A cuts ties with Instance B and C so people with accounts on Instance B and C can no longer read what is published on Instance A)

This is not how it works.

You can browse all instances without even having an account on any of them so absolutely noone loses access to anything. The only thing you temporarily(!) lose is the ability to WRITE anything on the defederated instance, but you can just make an account there anytime you want.

So when Instance A cuts ties with Instance B and C, people with accounts on A can no longer WRITE anything in communities on B and C, but everyone can still READ everything, and if you happen to have an account on Instance B and want to write something on Instance A, you can just create an account there.

Spending ten seconds on creating an account is not censorship.